Exhaust aftertreatment systems include components used to process exhaust gasses produced by an internal combustion engine for the purpose of reducing harmful exhaust emissions. Some aftertreatment system components, such as diesel oxidation catalysts (DOC) and selective catalytic reduction (SCR) catalysts, use catalytic materials to chemically convert potentially harmful exhaust emissions into other less harmful emission products. Such catalyst-based exhaust aftertreatment system components are desirable for their ability to efficiently control emissions. Unfortunately, some catalyst-based exhaust aftertreatment system components are also susceptible to damage from adverse operational and environmental conditions
For example, many components have an acceptable operating temperature range. Exceeding the upper limits of the temperature range can result in release of undesirable oxides, such as pentoxide being released from a Vanadium-based catalyst. On the other hand, operating at temperatures below the lower limits of the temperature range can result in unburned hydrocarbon being trapped or absorbed in the catalyst. Significant quantities of unburned hydrocarbon can become combustible, and pose a threat to aftertreatment hardware and the environment, due to uncontrolled thermal events
Another potential hazard to catalyst-based exhaust aftertreatment system components is the use of high sulfur-content fuels. Many of the catalysts used in exhaust aftertreatment systems include catalytic materials capable of oxidizing sulfur. Consequently, due to sulfur poisoning, fuels having high sulfur content can overwhelm and deactivate a catalyst configured to oxidize other emissions components.
Engine failures are yet another hazard to the components of exhaust aftertreatment systems. A bearing seal failure, for instance, might release oil into the exhaust line that could damage the components of an exhaust aftertreatment system.